Field of the Disclosure
The present disclosure generally relates to a telemetry operated ball release system.
Description of the Related Art
A wellbore is formed to access hydrocarbon bearing formations, e.g. crude oil and/or natural gas, by the use of drilling. Drilling is accomplished by utilizing a drill bit that is mounted on the end of a tubular string, such as a drill string. To drill within the wellbore to a predetermined depth, the drill string is often rotated by a top drive or rotary table on a surface platform or rig, and/or by a downhole motor mounted towards the lower end of the drill string. After drilling to a predetermined depth, the drill string and drill bit are removed and a section of casing is lowered into the wellbore. An annulus is thus formed between the string of casing and the formation. The casing string is cemented into the wellbore by circulating cement into the annulus defined between the outer wall of the casing and the borehole. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.
It is common to employ more than one string of casing or liner in a wellbore. In this respect, the well is drilled to a first designated depth with a drill bit on a drill string. The drill string is removed. A first string of casing is then run into the wellbore and set in the drilled out portion of the wellbore, and cement is circulated into the annulus behind the casing string. Next, the well is drilled to a second designated depth, and a second string of casing or liner, is run into the drilled out portion of the wellbore. If the second string is a liner string, the liner is set at a depth such that the upper portion of the second string of casing overlaps the lower portion of the first string of casing. The liner string may then be hung off of the existing casing. The second casing or liner string is then cemented. This process is typically repeated with additional casing or liner strings until the well has been drilled to total depth. In this manner, wells are typically formed with two or more strings of casing/liner of an ever-decreasing diameter.
A ball seat may be used to facilitate the coupling of liner strings by facilitating pressure increases within a bore of a liner to set a liner hanger in a casing, once a particular pressured is reached within the bore. A ball may be pumped from surface to the seat and pressure may be exerted on the seated ball to achieve a first predetermined pressure that sets a liner hanger. Once the liner hanger has been set, it is necessary to release the ball from the seat to restore circulation. Traditional ball seats use shear type devices to release the ball. Once the liner hanger has been set, then pressure can be increased to a second predetermined pressure which fractures the shear devices and releases the ball to restore circulation in the well. Traditional ball seats, however, suffer from several shortcomings. First, the shear values required to release the ball from the ball seat can vary greatly, and thus, the ball can inadvertently be released at an undesired pressure. Secondly, in some instances, hydrostatic pressure volume can be so great that landing of the ball on the seat is never detected. In such a case, a ball can land on a ball seat and shear so quickly that a pressure spike indicating isolation is never observed.